body {
    text-align: center;
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    margin: 0;
    padding: 0;
}

#header {
    display: flex;
    justify-content: space-between;
    padding: 15px 20px;
    font-size: 18px;
    font-weight: bold;
    background-color: #333;
    color: white;
}

#gameContainer {
    display: grid;
    grid-template-columns: repeat(4, 80px);
    gap: 10px;
    justify-content: center;
    margin-top: 20px;
}

.card {
    width: 80px;
    height: 80px;
    background-color: #008CBA;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    color: white;
    cursor: pointer;
    border-radius: 5px;
    user-select: none;
}

.flipped {
    background-color: #fff;
    color: black;
}

/* Popup styles */
#popup {
    display: none;
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: white;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.3);
    text-align: center;
}

#popup button {
    padding: 10px 20px;
    margin-top: 10px;
    font-size: 16px;
    background-color: #28a745;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}